The most common type of existing internal combustion engines include pistons connected via conrods to a crankshaft, whereby the pistons reciprocate cyclically within respective cylinders to perform the functions of induction, compression, expansion and exhaust of the working fluid.
Work is extracted from the working fluid by the combustion process wherein the expanding combusted gases resulting from combustion of the compressed working fluid forces the piston through the cylinder forcing rotation of the crankshaft.
The rotating mass of the crankshaft enables energy to be stored. The stored energy is applied to enable the piston to perform work on the working fluid in order to compress it prior to the combustion process. The work performed during compression, which is hereinafter referred to as “negative” work, reduces the total work which can be extracted via the engine's crankshaft.
This “negative” work is significantly increased if the combustion process commences during the compression process. In addition, any heat loss from the products of combustion of the working fluid are energy losses which cannot be converted into useful work extractable from the crankshaft.
In conventional engines the rate of change of the combustion chamber's volume during compression and expansion varies identically and sinusoidally. That is, the time-volume function of the combustion chamber, which is directly related to the time-displacement function of the piston, is sinusoidal. In particular, the piston has greatest velocity during the middle of each stroke and instantaneously zero velocity at the top and bottom of each stroke.
However, in the combustion process pressure increases rapidly due to the rapid production of combustion gases. The combustion gases then behave substantially in accordance with the gas laws. The result in conventional engines is a non-adiabatic expansion of the combustion gases as the initial slow movement of the piston and thus expansion of the working chamber prevents initial fast expansion of the working fluid.
The slow initial movement of the piston results in significant pressure and temperature increases which are believed to cause consequent massive heat losses through the walls of the working chamber. Accordingly the efficiency of the conventional petrol engine in converting chemical energy released by combustion into useable mechanical energy is only about 25%.
In effect, the conventional crankshaft driven piston is systematically misplaced throughout its cycle in relation to the behaviour of the products of combustion. While it is possible to vary, for example, the stroke length of the sinusoidal motion of the piston in the engine cylinder of a conventional engine, no modification will alter time-displacement function of the piston, and hence the time-volume function of the combustion chamber, from being sinusoidal in form. Accordingly it is not possible to readily alter a conventional engine so that the time-displacement function is not sinusoidal but is of some other form which may provide for greater engine efficiency.
Furthermore, while the crankshaft mechanism for internal combustion engines has many desirable features, such as simplicity, strength and reliability, it has mechanical disadvantages such as being unbalanced resulting in vibration.
The present invention aims to provide an internal combustion engine which is configured to allow the time-displacement function of the combustion chamber to be changed by a straightforward modification.